Objective: To empirically test the Rasch UE motor ability measurement framework. Background: The overwhelming majority of Veterans who survive stroke are unable to fully re-engage in meaningful activities because of persistent UE motor impairment. While advances from neuroscience are spurring development of new rehabilitation strategies, testing new strategies requires accurate quantification of impairment level in order to determine if a person is appropriate for a therapy and whether they have benefitted. It is essential to maximize and tailor rehabilitative strategies to an individual's specific impairments. However, currently, thereis no comprehensive evidence-based framework for objectively quantifying post-stroke UE motor ability (level of impairment), matching therapy to impairment level, or measuring specific therapy effects. Therefore there has not been a rehabilitation trial testing the effects of a therapy where a measurement framework is the basis for designing the treatment not only defining the outcome. In applying Rasch analysis, to the FMA-UE, we developed the Rasch UE motor ability measurement framework that locates a patient along a continuum of impairment and identifies the next steps in the recovery process. The purpose of this proposed research is to empirically test this framework. Methods: This is a double blinded randomized study with parallel arm design, stratified sampling and blocked randomization. 120 individuals with post-stroke UE hemiparesis will be enrolled; 40 participants per 3 UE impairment levels as defined by the Rasch FMA-UE measurement framework. Participants will undergo Rasch FMA-UE assessment each week for 4 weeks (pre-, day 7, mid-, day 21 and post-treatment) and assessments of 3D unconstrained reaching at 3 time points (pre-, mid-, post- treatment) and engage in 12 sessions (3x/week for 4 weeks, 2 hrs/session) of reach-to-grasp task-practice. Within each impairment level, subjects will be randomized to a treatment group; 20 subjects will receive targeted task-practice and 20 subjects will receive non-targeted task-practice. Targeted task-practice is tailored to patient-specific UE motor deficits with initial targets (goals) defind according to baseline Rasch FMA-UE measures and targets continually progressed after every 3 therapy sessions so that the goals match the patient's evolving level of ability. Non-targeted task practice is defined as a standard of care task-practice intervention intended to increase UE use but not alter specific impairments. Data analyses will include (1) ANOVA to test the effects of targeted vs. non-targeted therapy on UE motor ability, (2) multiple regression to model the relationship between therapy and movement adaptions occurring pre- to post-rehabilitation, and (3) growth mixture modeling to define responders and non-responders. Hypotheses: Therapeutic task practice at the just-right challenge of difficulty will maximize post-stroke moto skill reacquisition. We expect that targeted practice, will increase UE motor ability because the difficulty of task goals will be matched and systematically progressed according to patients' initial and evolving levels of ability. Significance: The need for novel interventions to improve the function of Veterans who sustain stroke is important. Many new rehabilitation strategies are being developed and tested. Standardized assessments are used to define the value of these new strategies. However, most widely used standardized assessments are inadequate because they fail to clearly measure baseline ability or define treatment response, as a result, do not inform treatment decisions. Therefore measurement is disconnected from treatment planning. Unfortunately the development of novel measurement methods has not kept pace with the development of novel interventions. We strongly believe that new measurement methods are needed, particularly those that both prescribe treatment and monitor outcomes. If this Merit Review is successful, the Rasch UE ability framework will lead to future studies aimed at 1) implementing the Rasch FMA-UE framework into clinical practice for theoretically-grounded treatment planning decisions, and 2) refining targeted UE treatments for improved treatment efficacy.